Synthetic genomes with altered genetic codes

The genetic code is the set of rules that define how information encoded in DNA is interpreted into amino acids to make pro-teins. With few naturally occurring exceptions, the vast majority of living organisms share the same genetic code. Recently, however, technological advances in DNA synthesis, sequencing and genome engineering are enabling the devel-opment of synthetic genomes with drastically altered genetic codes. Such comprehensive genome modifications endow these unnatural organisms with unique capabilities such as genetic isolation, virus resistance, and production of proteins with novel functionality. Here, we summarize recent efforts to develop alternative genetic codes, explore technical and bio-logical challenges for alterations performed at whole chromo-some scale, and discuss the impact of synthetic organisms for biological research and biotechnology.